The makeshift memorial for slain teenager Trayvon Martin continues to grow daily outside of the Retreat at Twin Lakes community in Sanford, Florida.

Red Huber/MCT/Landov

A huge part of the Trayvon Martin story is of course about race. The killing of the unarmed, black teenager has led to conversations about biases against black men. In a lot of ways it fits the stories that we've heard so many times before: A black man was profiled by a white man and the authorities won't step in to and provide justice for a black victim.

But there is one element of this story that complicates that narrative: While, George Zimmerman, the alleged gunman, has been identified by most media as white, his father told the Orlando Sentinelthat he is a "Spanish-speaking minority," from a multiracial family. Zimmerman could be Latino. For all we know, he could be of Afro-Caribbean descent.

We wondered, if that turned out to be the case, how would the framing of this story change? Would it still be considered a "hate crime" by some? Would it have boiled up to the national level at all?

So we spoke to Joshua Correll, a University of Chicago psychology professor who has for years studied bias against black men. His line of study specifically looks at bias when people are making decisions whether to pull a trigger on a bad guy.

Correll says the participants are universally more likely to fire at black men — whether the shooter is young, old, male, female or even black.

"Our working hypothesis is that in American culture, black is often associated with danger and crime and physical aggression," Correll says. "And it's really that association that leads us to see them as a greater threat and to pull the trigger. And everybody knows about those stereotypes. You don't need to be black or white or Latino or Asian to learn about those stereotypes. We all see them all the time, in news coverage, in movies, in a lot of music."

Correll, who is white, has been testing this hypothesis since 2002. Mostly, he's looked at bias when police officers decided to shoot, but he has also tested other members of the community. (Obviously none of these tests are directly connected to the Florida shooting.)

Here's how his test works: He gives the participant two buttons: Shoot or don't shoot. Then he presents pictures of black men and white men. Some are holding guns, others are holding harmless things like wallets and cellphones. The point is to shoot the guys with guns. What Correll has found is that no matter the race or the age of the shooter, he or she is more likely to fire at an unarmed black man. They're also less likely to shoot an armed white man.

"Everybody was faster to shoot a black target than a white target, and the magnitude of that bias was equivalent" regardless of race, said Correll.

On Tell Me More today, Michael Skolnik, co-president of the cultural website Global Grind (founded by hip-hop pioneer Russell Simmons), riffed on this same theme. He made the case that Martin's killing underscores why white Americans must "stand up with" blacks and other minorities at times such as this.

From 'Tell Me More'

An African-American kid such as Martin, Skolnik told Tell Me More's Michel Martin, can be singled out for looking "suspicious." But, as he wrote in his essay, "Even if I have a black hoodie, a pair of jeans and white sneakers on ... in fact, that is what I wore yesterday ... I still will never look suspicious."

Correll points out another important point of his research: Age hasn't mattered in his research. So, participants who grew up in a more overtly racist time were just as likely to shoot the black target as younger participants who have grown up in a country that just elected its first black president.

It's a bleak landscape, Correll admits, and he hasn't found any evidence that cultural sensitivity training curbs people's biases.

"To the extent that we're all exposed to [these biases], it becomes a tricky situation," says Correll.